Large surfaces to be paved require multiple passes of the paving apparatus, including a screed for leveling a layer of bituminous concrete, typically referred to as blacktop. The layer of blacktop along the edge of a paving swath against which a subsequent swath of blacktop is to be laid is typically formed with a joint to facilitate the joinder of the adjacent layers of blacktop. The joint is formed by a screed extension that is shaped into the desired joint configuration. Compaction of the bituminous concrete is accomplished primarily by motorized roller machines passing back and forth over the layer of blacktop previously laid. Motorized roller machines cannot roll over the joint portion of the blacktop layer as the compaction action would destroy the configuration of the joint.
Bituminous concrete is typically applied in layers, referred to as courses, with a base layer being deposited over a stone base or other support, followed by a wear course deposited over the top surface of the base course. The blacktop is trucked to a screed that deposits the blacktop in a course having a predetermined thickness. Since the screeds have a discrete width, large surfaces to be covered require two or more passes with the screed laying adjacent swaths of blacktop with each pass. As shown in FIG. 2, the wedge notch joint 2 is formed along a side of a swath 1 of blacktop for the merger of the adjacent swaths of blacktop and typically has a configuration specified by contract specifications. The wedge notch joint 2 is typically configured with an upper lip 3 defining an edge having a depth of perhaps one-half inch, the actual depth being determined by the size of aggregate being used in the blacktop being deposited as the height being at least the maximum size of the aggregate. The joint 2 then has a sloped portion 5 that extends from the upper lip 3 downwardly to a lower lip 7 that forms an edge having a height at least as great as the maximum size of the aggregate used in the course of blacktop being deposited in the adjacent swath.
This joint configuration provides for a smooth joinder of adjacent swaths of blacktop. Compaction of the joint area is accomplished after the adjacent layer of blacktop is deposited so that the motorized roller machine is run over top of the joinder area. The problem arises with the first swath of blacktop from which the joint is formed cures before the subsequent swath is applied on top of the joint and the motorized roller machines are ineffective to compact the cured joint on the first swath. When compaction tests are performed, the joint area is typically the primary locations at which the compaction tests fail.
It would be desirable to provide a screed extension that would be operable to form a joint for the merger of adjacent swaths of a blacktop course in the desired configuration, but with an ability to compact the joint area when the swath on which the joint is formed is deposited, and before the application of the adjacent swath of blacktop.